With the advancement in technologies, object tracking and trajectory reconstruction have been widely used in, for example, traffic accident reconstruction, navigation of aerocrafts and trajectory evaluation, positioning aiding and game control. In object tracking and trajectory reconstruction, the rotational angle and the displacement of the object are given with the use of inertial measurement units.
Conventionally, an object tracking and trajectory reconstruction system generally comprises inertial measurement units. The inertial measurement units may comprise a gyroscope, an accelerometer and a magnetic compass. More particularly, the gyroscope is capable of detecting the angular velocity to calculate the rotational angle of an object. The accelerometer is capable of detecting the acceleration to calculate the displacement of the object. The magnetic compass is capable of detecting the absolute orientation to obtain the rotational angle of the object.
In U.S. Pub. No. 2008/0046214, a sensor system is disclosed using gyroscopes, accelerometers and magnetic compasses to detect the orientation and status of an object. Moreover, U.S. Pat. No. 4,038,527 also discloses a technology for detecting the status and the orientation of a movable object using gyroscopes and accelerometers. Moreover, U.S. Pat. No. 6,842,991 also discloses a technology for detecting the status and the orientation of a movable object using gyroscopes and magnetic compasses. However, since the gyroscope is expensive, it is not suitable for daily use. The magnetic compass is easily interfered with surrounding electronic appliances.
In U.S. Pat. No. 5,615,132, a technology for detecting the position and the orientation of an object using six linear accelerometers is disclosed. In U.S. Pat. No. 5,615,132, six accelerometers are used to detect three-dimensional motion status and the orientation of an object. When four accelerometers are used, two-dimensional motion status and the orientation of an object can be detected. Moreover, Chen et al. also disclose a motion status detection technology using six linear accelerometers, entitled “Gyroscope free strapdown inertial measurement unit by six linear accelerometers”, (Journal of Guidance, Control, and Dynamics 1994 0731-5090 vol. 17 no. 2(285-290)). More particularly, the six accelerometers are respectively disposed at the center of each edge of a regular tetrahedron. Each of the accelerometers is required to be fixedly positioned and oriented to detect the status and position of the object.